<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        do {
        var user = prompt ( '请输入用户名:' );
        var stn = prompt ( '请输入密码:' );
        } while (user !== 'admin' && stn !== '123456' );
        alert ( '登录成功')
        </script>
</body>
</html>